1990 Chevy Truck clutch

I just bought this truck yesterday 1990 chevy k1500 five speed manual transmission, it just had a new clutch and throwout bearing installed and has ben driven about two miles since the new clutch, the truck takes off perfect and works great the truck shifts into every gear accept third when you shift it into third gear everytime no matter what speed or rpm it grinds into gear could this just be the new clutch hasn't set in yet? Or something different?